1. Field of the Invention
The present invention relates to a gas friction pump including a housing having a suction opening connectable with a recipient, and a gas outlet opening, and a plurality of pumping active rotor and stator components arranged in the housing for delivery of gases and for producing a compression ratio, with the rotor and stator components having a diameter larger than a diameter of the suction opening.
2. Description of the Prior Art
For delivery of gases, gas friction pumps of different types are used. The gas friction pump operates in a molecular flow region, and its operation is based on transmission of pulses of movable walls to gas particles. A first gas friction pump of this type was developed by German scientist and engineer Gaede. The gas friction pump was further modified, without altering its basic principle, by German engineers Siegbahn, Holweck, and Becker. The latest modification is known as a turbomolecular pump. The turbomolecular pump found a wide application in science and industry, and the present invention is described with reference to a turbomolecular pump.
The below described drawbacks of the conventional turbomolecular pumps and elimination of these drawbacks by the present invention are equally applicable to other types of gas friction pumps.
The suction capacity of the turbomolecular pumps is determined, in addition to their inner structure and the rotational speed, by the inlet cross-section of the suction flange. The dimensions of the suction flange, in accordance with existing standards, is established at a somewhat smaller value. If with so predetermined suction cross-section, a larger suction capacity need be achieved, the diameter of the stator and rotor discs and, thus, the pumping active surface can be increased. This results in a structure in which the rotor and stator disc diameter is larger than the diameter of the suction flange. It is obvious that the suction capacity is limited by the cross-section of the suction flange. The reduced cross-section of the suction flange finctions as flow resistance between the uppermost rotor disc and the recipient.
Accordingly, the object of the present invention is to provide means that would permit to overcome this flow resistance to a most possible extent in order to be able to use the suction capacity, which is predetermined by the upper rotor disc, to a maximum.
This and other object of the present invention, which will become apparent hereinafter, are achieved by providing a modified rotor component located adjacent to the suction opening and having a gas delivery structure. The modified rotor component has a radial extent which increases starting from the suction opening in a direction of a radial extent of the pumping active rotor and stator components and which can attain the radial extent of the pumping active rotor and stator components.
The modified rotor component permits to reduce the conductance losses, which are caused by the reduced predetermined diameter of the suction flange, to a most possible extent. The pumped-out gas is fed from the recipient through the gas delivery structure of the conventional, large diameter rotor and stator components further without any losses.
By selecting an appropriate profile of the modified rotor component stepped, conical, dome-shaped, etc . . . , the modified rotor component can be optimally adapted to the recipient and to the connection of the recipient with the suction flange. The modified rotor component can be so formed that it would extend through the suction opening and into the recipient.
The present invention contemplates arranging in the pump housing of stator components with pumping active structure opposite the modified rotor component. These stator components permit to effectively form an optimal transition from smaller diameters to larger diameters.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.